Thermally stable beta alloys of titanium



United States 2,754,203 Patented July 10, 1955 Free THERMALLY STABLE BETA ALLOYS F TITANIUM Milton B. Vordahl, Beaver, Pa., assignor to Rem-Cm Titanium, Inc., Midland, Pa., a corporation of Pennsylvania No Drawing. Application May 22, 1953, Serial No. 356,877

18 Claims. (Cl. 75-1755) This invention pertains to strong, ductile and thermally stable titanium-base alloys having a substantially all-beta microstructure, and containing at least one element'selected from the group consisting of vanadium, molybdenum, columbium and tantalum, the preferred element of this group being vanadium.

The preferred alloys of the invention contain a plurality of alloying elements selected from the group consisting of beta-promoters and alpha-promoters which impart sluggishness to beta decomposition, such as tin, aluminum and antimony.

This application is a continuation-in-part of my co-pending applications S. N. 318,309, filed November 1, 1952, and S. N. 323,155, filed November 28, 1952.

As is known, the metal titanium in the pure state is capable of existing in either of two allotropic forms. Below a temperature of 885 C., it assumes a close-packed hexagonal microstructure known as the alpha phase, While at this temperature and above, it assumes a body-centered cubic microstructure known as the beta phase.

Certain substitutional alloying additions to the titaniumbase metal tend to promote or stabilize the alpha phase. Elements ordinarily grouped in this category are aluminum, tin, antimony, indium, bismuth, lead, cadmium, zinc, thallium, as well as the interstitials carbon, oxygen and nitrogen. A common characteristic of all alpha stabilizers is that little or no hardening of the alloy ocurs in thermal processing or aging. The resulting alloys are always allalpha in microstructure regardless of the heat treatment, including quenching or aging. above listed all fit into this category in that they all form all-alpha alloys which do not retain any substantial content of the beta phase nor harden appreciably on quenching from the beta field.

Other substitutional alloying elements, when added in progressively increasing quantities, stabilize the beta phase at progressively lower temperatures, until a mixed alphabeta' or stable all-beta microstructure is obtained at normal or atmospheric temperatures, or the beta phase undergoes an eutectoid reaction, depending on the character and amount of the beta stabilizers added. Speaking in broadest terms, the beta stabilizers are molybdenum, vanadium, columbium, tantalum, zirconium, manganese, iron, chro- The alloying elements mium, tungsten, copper, cobalt, nickel, silicon and beryllium. Of this group, molybdenum, vanadium, columbium and tantalum are beta-isomorphous with titanium, and hence form no eutectoid decomposition products on aging. Zirconium is isomorphous with titanium in both the alpha and beta fields. Zirconium, however, merely lowers the transformation temperature of titanium, but the alloys eventually revert to the alpha phase at low temperatures unless other betal promoters are present. Thus it is proper to consider zirconium together with vanadium, molybdenum, columbium and tantalum as all being beta-isomorphous with titanium.

The remaining elements in the broad category of beta promoters above mentioned are all eutectoid formers with titanium, i. e., they decompose on aging into eutectoid decomposition products. However, manganese, chromium and iron are so sluggishly reactive in this respect, that they behave in general like the elements of the beta-isomorphous system. Tungsten, copper, cobalt, nickel, silicon and beryllium decompose rapidly into eutectoid products, silicon and beryllium so rapidly in fact, that it is entirely proper to group them as compound-formers along with such strictly compound-forming alloying additions as cerium, boron, arsenic, sulfur, tellurium and phosphorus. The compound-formers have low solubility in either the alpha or beta phase, but form intermetallic compounds with titanium.

In my aforesaid parent application Serial No. 323,155, I have disclosed a series of strong, ductile, thermally stable and tear-resistant titanium-base alloys, having a mixed phase, alpha-beta microstructure obtained by alloying with a titanium-base metal of commercial purity, about 112% of beta-promoting elements of the group vanadium, molybdenum, columbium and tantalum, said alloy containing, preferably, a plurality of elements of this group, or at least one element of this group together with at least 1% of other elements, including alpha-promoters such as tin and aluminum or beta promoters such as chromium, manganese and iron.

In my parent application Serial No. 318,309, I have disclosed a series of strong, ductile and thermally stable titanium-base alloys having a substantially all-beta microstructure, obtained by alloying with titanium-base metal of commercial purity, about l020%, .and preferably about 12-17%, of beta-promoting elements together with about 210%, and preferably about 3-7%, tin. The preferred beta-promoting additions of said application are those of the beta-isomorphous and sluggishly eutectoid groups aforesaid. As pointed out in said application, a titanium-base alloy containing a relatively low aggregate content of beta-promoting elements within the range aforesaid, namely, about 1020%, is normally thermally unstable in the absence of the tin addition referred to. That is to say, although these alloys have a substantially all-beta microstructure on rapidly cooling or quenching from the beta field, nevertheless on subsequent aging at temperatures of about 400800 5., they revert to an alpha-beta microstructure or to a mixed structure containing eutectoid decomposition products, depending on the beta-promoter additions present. The addition to such alloys, of tin within the broad range of about 210% aforesaid and preferably 37%, has a stabilizing action on such alloys in that it imparts sluggishness to the beta decomposition, despite the fact that tin is generally regarded as an alpha-promoter or stabilizer and does not itself form a'eutectoid with titanium. As further pointed out in said application, the best alloys thereof are obtained with a multiplicity of beta-promoters along with tin. It is also brought out that the tin addition provides effectively stable beta alloys at lower aggregate contents of the beta-promoters which produce eutectoid decomposition, than is obtainable in the absence of tin, the tin addition also effectively thermally stabilizing many of the beta analyses which would otherwise be unstable on aging.

Now in accordance with the present invention, I have discovered a further series of strong, ductile and thermally stable titanium-base alloys having a substantially all-beta microstructure, which in general require no additions of tin or equivalent alpha-promoters for stabilizing the beta structure. In one of its broadest aspects this new series of alloys is obtained by alloying with titanium-base metal of commercial purity, from about 20% to.50%. of beta-promoting elements, including at least 15% of one or more elements selected from the beta-isomorphous group vanadium, molybdenum, columbium and tantalum, the preferred element of this group being vanadium. However, for those alloys of this series in which the elements of the beta-isomorphous group present are wholly or substantially vanadium and/or molybdenum, the total content of beta promoters present may range as low as about and the total con- 4- tility and hardness values after various aging, heat treatments. As is now well known, titanium-base alloys having an all-beta microstructure, are characterized by a high degree of ductility and correspondingly relatively tent of beta-isomorphous promoters present may like- 6 low degree of hardness. Thermally stable beta alloys wise range as low as about 10%, as shown by the test are characterized in undergoing no substantial change results given in Table 1, below. The best of this new or reduction in ductility or increase in hardness on proseries of alloys are those containing a plurality of beta longed aging at elevated temperatures, within the range, promoters. These may be selected exclusively from the for example, of about 400800 F. A radical change in beta-isomorphous group, or may be selected in part from 10 hardness as a result of such aging heat treatment shows this group and in part from the eutectoid group aforesaid. that the alloy is thermally unstable. In this connection, If eutectoid beta-promoters are present, their aggregate my experimentson beta, titanium-base alloys, indicate content should not exceed the total content of the betathat while alpha separation resulting from overaging does isomorphous elements present and in any event, the tonot necessarily impair ductility seriously, the same is not tal content of eutectoid beta-promoters should not exceed true with respect to eutectoid decomposition, which alabout 15%, and in general will not exceed about 10%. Ways results in increasing embrittlement. As to hard- Also as above noted, the total content of beta-isomorness, an increase in hardness without drastic loss of bend pnous promoters present should not be less than about ductility as a result of aging, is considered a promising 15%. indication for a heat treatable beta alloy. It has been Subject to the foregoing restrictions, the sluggishly found, however, that any hardness increase by aging alone eutectoid beta-promoters chromium, manganese and iron which is substantially in excess of Rockwell A 70, is may be more or less freely substituted for those of the almost invariably associated with more or less complete beta-isomorphous group. On the other hand, the rapidly embrittlement. eutectoid beta-promoters tungsten, copper, cobalt and For the foregoing reasons, in the test results set forth nickel can be tolerated to only a limited extent, i. e., not in the following Table I, thesetwo criteria have been over about 5% in aggregate, and preferably not more employed as indicative of the thermal stability of the than about 2%. As to the strictly compound-formers, alloys according to the invention. with which are grouped silicon and beryllium, their to- In Table I, the columns headed S give the bend (31 c nten ld Bev l: ed a ut 2% a ductility and hardness values of the various analyses in The alloys of thls lflventlPn contamins P t of 0 the as rolled and annealed condition, i. e., after rolling 0f beta-Promoters require 110 addltlons at 1400 F. to an intermediate gauge, followed by cleanl j fi a g l tl 'l ij for Stablhzmg the ing and further rolling at 1300 F. to final gauge, folut W ere eta'promoter lowed by holding one hour at 1300 F., furnace cooling tent is under 20%, the addition of about 210%, and th 3 ence to 1100 F., and air cooling to room temperapreferably about 27%, tin, and/or about 1-8%, and

V ture. The columns headed T give the corresponding preferably about 2-5%, aluminum, 1s required for efv 1 f th a1 it h fective beta stabilization. As regards such alloys, antiues ese g? f, 3 er 160mg t 6 same mony has about the same stabilizing action as tin when m the mmal men to an agmg E i f for substituted therefor in about the same percentage. 24 at 750 The F headed P The tolerance of these alloys for the interstitials is 40 responfimg Values 5 3 the analyses the mmal relatively low and should not exceed about 0.3% for condmon s for Perlod of 100 hours at carbon, 0.2% for oxygen or 0.1% for nitrogen. correspondingly, the Columns headed g thfi The thermal stability of the alloys according to the inresp g Values after aging the analyses in the initial vention is best determined by measuring their bend duccondition S for 100 hours at 500 F.

Table I COMPOSITION, Percent (Balance Titanium) Ductility and Hardn%ssdiin1le1t Treated Condition 11 CB'B Minimum Bend Ductility T Hardness Rockwell A V Mo Cr Mn Fe Sn Al Other V s '1 U L s T U L 3 70 25 1 1 4.1 6 54 64 62 1.3 4.3 6 52 59 15 5 3.3 7 64 7o 5.3 7 64 71 10 10 7 7 71 73 7 B 63 73 15 5 7 B 73 73 7 B 74 72 20 5 1.4 4.6 7 57 67 65 1.7 6.2 7 56 67 63 COMPOSITION, Percent (Balance Titanium) Ductillty'and Hardness in Heat TreatedConditlon Indicated Minimum Bend Ductility T Hardness Rockwell A V Mo Cr Mn Fe Sn Al Other- S T U L S T U L 20 5 1.8 7 B B 54 74 74 73 1. 8 B B 65 73 75 71 1O 5 5 0.9 1.2 6 0.9 64 64 r 74 63 0.9 1.3 7 0.9 63 64 73 63 20 5 5 5.1 6 B 3.8 63 73 75 62 5. 3 6 B 4.0 64 72 74 64 5 5 .5 6 6 13 6 68 71 75 68 6 6 B 6 68 71 7 5 68 5 10Zr 1. 9 7 B B 60 63 75 74 3. 4 7 B B 60 64 75 74 10 5 6 6 7 7 70 73 72 73 6.2 7 7 8 69 73 74 73 15 5 5 1.3 63 66 1.3 64 64 65 65 1. 2 6. 4 7. 8 1. 1 65 66 65 65 10 5 5 1. 9 71 7 3. 2 64 67 72 65 1. 8 7. 1 7. 2 4. 5 64 66 71 67 10 10 5 1. 8 7. 1 7 2. 6 67 67 67 67 1. 6 61 6. 5 2.3 66 67 67 67 15 10 5 1. 6 4. 4 63 1 9 67 68 69 68 1. 2 6. 1 2. 4 67 68 68 68 1 1 5 l) 15 5 5 5N1 2. 4 3. 3 6. 5 3. 5 64 66 a 65 65 3. 2 6. 5 6. 5 2. 5 64 66 66 65 5 5 15Ta 1.4 6.3 7.4 7.8 66 67 73 71 1. 5 7. 6 7. 4 65 67 72 71 5 5 15Gb 3.7 7.2 7.2 4.8 65 65 71 65 3.0 7. 6 7.4 4.1 65 66 70 65 5 15'la B B 5 5 15Ta 11; 15 5 5 2Ni 1. 7 5. 8 6. 1 1.2 63 63 69 63 1. 6 6 6. 5 1. 8 62 63 67 61 15 5 5 5C11 1. 7 6 7 7. 2 64 70 70 72 1.3 6. 6 6. 6 5.0 64 69 70 79 15 5 5 2Cu 1. 8 7. 4 7. 4 '1. 8 62 63 69 61 1.8 6. 8 7. 2 7. 6 61 61 67 63 35 1.0 4.2 2.2 1.0 54 55 54 57 1. 4 4.3 2.4 0.6 57 55 54 56 12 5 3. 6 5. 2 3.9 62 65 56 9 4.5 4.6 4.7 5.5 63 63 64 9 6.5 5.2 3.8 4.6 63 65 67 12 2 4. 9 3.2 6.1 65 65 67 13.5 4.5 3.5 3.9 6.4 63 66 69 1 Broke up in rolling at 1400 F.

I All broke up in rolling at 1600 F. 5 Broke up in rolling at 1600 F.' Broke up in rolling.

Referring to the above data, it will be observed that the binary alloys of the beta-isomorphous group are not efiectively stable below about 25% of the alloying constituents. This is shown by the data for the titaniumvanadium binary, which at the vanadium level, is quite brittle and hard even in the as rolled and annealed condition. At the vanadium level the alloy undergoes a rather marked increase in bend ductility and hardness as a result of aging from the condition S to the condition L, although its ductility and hardness in the T aged condition is acceptable. At the vanadium level, however, the alloy undergoes substantially no change in bend ductility or hardness even after prolonged aging, the bend ductility being on the order of l-2 T, as rolled and annealed and also after aging 100 hours at 500 or 750 F., and the hardness remaining substantially constant at about 54-57 Rockwell A. However, at the 35% and higher vanadium levels, this binary alloy undergoes an objectionable degree of scaling, the scaling at 1300 F. being quite high. To prevent this, the addition of a scale reducing beta-promoter'such as chromium is necessary. In addition, the binary alloys are quite low in tensile strength. The tensile properties are sharply increased by additions of alpha-promoters such as tin or aluminum.

For these reasons, the preferred and best alloys of the invention are the ternary and higher component analyses containing a multiplicity of beta-promoters, including at least one of the beta-isomorphous group, .or containing at least one promoter of :the 'beta-isomorphous group together with an alpha-promoter such as tin or aluminum which imparts sluggishness to the beta decomposition, or

containing a multiplicity of beta-promoters as aforesaid as well as one or more alpha-promoters. This is well substantiated .by the test data given in the table for the ternary and higher component analyses as compared to the binary analyses. Thus the 25V5Sn 2.5Al alloy has the extremely good bend ductility of only 0.3T in the as rolled and annealed condition, and substantially the same value, i. e., 0.9 T after aging for 24 hours at 500 F., and only a slightly higher value of 1.6 Tafter aging 1 00 hours at 750 F. The hardness remains substantially constant at about 59 Rockwell A. Similarly, the 15V-5Mo-5Mn alloy has an extremely low bend ductility of about 1 T or under in the as rolled and annealed condition which increases to only about 2 T after aging hours at 500 C. and only a slightly higher value of about 3-4 T after aging 100 hours at 750 F., the hardness remaining substantially constant at about 61-67 Rockwell A. Numerous other analyses containing a multiplicity of beta-promoters, or beta plus alphapromoters or both as aforesaid show correspondingly low and substantially constant bend ductilities and hardness values on aging from the as rolled and annealed condition, thus establishing their high degree of thermal stability.

As above stated, the alloys containing upwards of 20% of the beta-promoters, require no additions of the betastabilizing, alpha-promoters, such as tin, aluminum, etc. This is well illustrated for the l5V-5Mo5Mn analysis above referred to, as Well as by the 15V5Mo5Cr analysis, specifically to mention only two of the many similar analyses shown.

Also as above emphasized, the alloys containing 20% and under of the beta-promoters, require additions of the alpha-stabilizers tin, aluminum, etc., for eifective thermal stabilization of the beta phase as evidenced by comparison of the 15V-5Mo analysis, which was severely embrittled on aging, with the 15V-5Mo-5Sn analysis, the bend ductility of which in the as rolled and annealed condition is extremely good, i. e., 1-2 T and underwent no appreciable decrease on prolonged aging, being only 2-3 T after 100 hours at 500 F., and being only about 4-5 T after 100 hours at 750 F., with correspondingly low hardness changes from about 58 to 59 to 66.

As further above emphasized, vanadium is the preferred element of the beta-isomorphous group, as evidenced by the high degree of thermal stability obtained with the majority of the vanadium-containing alloys as compared to those in which other elements of the betaisomorphous group, such as tantalum and columbium are substituted for vanadium. The latter undergo considerable decrease in ductility and increase in hardness as a result of aging. Of even more controlling importance as regards this vanadium preference are: its low density or specific gravity as compared to tantalum or columbium, its greater abundance, and the relative ease with which it may be melted and alloyed with titanium as compared to columbium and tantalum.

It was pointed out above that, the preferred eutectoid additions are those of the sluggishly eutectoid type, i. e., chromium, manganese, or iron, which as shown by the data, give excellent results when substituted within the limits above stated for elements of the beta-isomorphous group. On the other hand, the rapidly eutectoid betapromoters such as copper, nickel, etc., tend to embrittle the alloys when present in amounts of upwards of about 2% in aggregate, as evidenced by the concluding data of the table.

Of the various analyses listed in the above table, the vast majority fall within the category of what I refer to as usefully stable beta alloys, while others fall additionally within the category of what I designate as effectively stable beta alloys. The expression usefully stable beta alloys refers to such alloys in the broadest sense. It includes beta alloys of barely sufficient stability to permit of normal processing including a short heating for leveling and descaling, plus extended use at normal atmospheric or room temperatures without becoming com pletely embrittled, i. e., glass brittle. The vast majority of the analyses listed in the above table would fall into this category, including all compositions which are not brittle in the as rolled and annealed or S condition, such for example as the 25V5Sn5Al analysis, or the lV-10Mo or 15V-5M0 analyses. The effectively stable beta alloys comprise only those which will withstand at least 100 hours service at a temperature in the range of 500800 F., without undergoing appreciable loss in ductility or becoming unduly embrittled. This group also includes the so-called heat treatable, stable beta alloys, i. e., those which will harden on aging at 700800 F. or even higher, but which will remain thermally stable when aged at 500 F. A heat treatable, stable beta alloy accordingly may be bent, stretched or otherwise hot or cold formed to shape, and thereupon aged to a desired hardness or strength at 750 F., and then be put into service at temperatures up to 500 F. without danger of further embrittlement. A number of such compositions can be found in the analyses of Table I.

As above emphasized, the controlling properties to be sought in the beta alloys are good ductility and thermal stability, i. e., retention of ductility on aging. The tensile properties of such alloys are not of controlling importance inasmuch as those obtainable with any given analysis within the effectively stable beta range, can be substantially duplicated with other analyses, involving relatively small adjustments as to composition or processing. This is illustrated in the data of the following Table 16 II wherein the tensile properties of a number of effectively stable beta alloys of different analyses, are compared:

Table II 5 Tensile Properties Composition, Percent (Balance Titanium) Ultimate Percent Strengt l 1, lj Jelrcent geduep. s. 1. ong. ion in 1,000 Area V5M050r-5Sn 143 17. O 40. 6 15V50r5Fe5Sn 152 18. 0 43. 1 15V5Fe-5Sn 132 18. 0 47. 7 15V-10Cr-2.5Al- 140 20. 0 50. 9 15 15V100r5Al 146 17.0 42. 2 15V-10Cr-2.5Al 161 13. 0 44. 0 10Mn5M05Cr 143 27. 0 47. 0 10Mn-5M0-C1 135 6.0 11. 5 8Mn-4Mo-40n-5Sn 138 19.0 52.0 7.5Mn-7.50r5Sn 135 16. 0 57. 0

It will be noted from the above data that whereas the compositions vary widely, the tensile properties fall within a reasonably compact range of values. Attention is also directed to the manner in which the strength level of the 15VlOCr analyses increases as additions of such alpha-promoters as aluminum and tin, while still retaining the alloy within the efiectively stable beta category above discussed. Thus, as stated, the ductility and thermal stability criteria of these beta alloys are of much perature tensile properties.

The alloys of the invention may be made by melt casting in a cold mold, employing an electric arc in an inertatmosphere, or may be produced in other ways in which the alloy is rendered molten before casting. The titanium base metal employed should be of acceptable purity, such as the commercial purity product obtained by magnesium reduction of titanium tetrachloride or equivalent procedures.

Where these alloys are to be used in the form of sheets, the minimum bend ductility may range as high as 20 T, and where the alloys are to be used in massive form, as in forgings, the percent tensile elongation may range as low as 1 to 2%.

Thus the invention comprises in broader aspect, an alloy containing about 15 to 50% of at least one beta promoter which is isomorphous with titanium, and at least 1%, and preferably at least 5%, of an element or elements selected from the groups consisting of addi tional beta promoters and of alpha promoters, which tend to stabilize the beta phase, such as tin, the alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

Where the alloy contains eutectoid beta-promoters along with those of the beta-isomorphous group, the minimum effective content of the eutectoid beta-promoters present, is about 1%, a preferred lower limit being about 5%. Where the alloy contains alpha-promoters, such as 60 tin, aluminum, etc., which tend to stabilize the beta phase,

the efiective lower limit is about 1% in the case of aluminum, and about 2% in the case of tin or antimony,

the upper limit for aluminum being about 8% and for tin or antimony about 10%.

What is claimed is:

1. An alloy consisting essentially of about: 20 to 50%v of at least one beta-promoter which is isomorphous with titanium and from at least 1% up to about 15% of an element selected from the group consisting of additional beta-promoters and alpha-promoters whichtend to stabilize the beta phase, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend duc tility of not over 20 T.

more fundamental importance than are the room tem-' aluminum, etc.,

2. 'An alloy consisting essentially of about: 20 to 50% of at least one beta-promoter which is isomorphous with titanium, and 1 to 15% of an alpha-promoter which tends to stabilize the beta phase, balance titanium, said alloy'being characterized by'high thermal stability and in having asnbstantially all-beta structure and a minimum bend ductility of not over 20 T. v

:3. An alloy consisting essentially of about: 20 to 50% of at least one beta-promoter which is isomorphous with titanium, and l to 15% of at least one eutectoid betapromoter, the total content of eutectoid beta-promoters present not exceeding the total content of the isomorphous beta-promoters present, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

4. An alloy consisting of: 20 to50% of at least one beta-promoter which is isomorphous with titanium, 1' to 15% of at least one eutectoid beta-promoter, the total content of the eutectoid beta-promoters present not exceeding the total content of the isomorphous beta-prometers present, balance titanium.

5. An alloy consisting of: 20 to 50% of at least one beta-promoter which is isomorphous with titanium, 1 to 15% of at least one alpha-promoter which tends to stabilize the beta phase, 1 to 15% of at least one eutectoid beta-promoter, the total content of eutectoid beta-promoters present not exceeding the total content of the isomorphous beta-promoters present, balance titanium.

6. An alloy consisting essentially of about: 20 to 50% of vanadium, l to 15 of an element selected from the group consisting of other beta-promoters and alpha-promoters which tend to stabilize the beta phase, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

7. An alloy consisting essentially of about: 20 to 50% of a plurality of beta-promoters, including at least 15 of at least one beta-promoter which is isomorphous with titanium, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T, i

8. An ,alloy consisting essentially of about: 20 to 50% oiat least one beta-promoter which is isomorphous with titanium, and at least 5 to about of at least one element selected from the group consisting of additional beta-promoters and alpha-promoters which tend to stabilize the beta'phase, said alloy being characterized in having a substantially all-beta structure, a minimum bend ductility of not over T, and in undergoing no appreciable change in ductility and hardness on aging 100'hours atSOO" F. i

'9. An alloy consisting essentially of about: ,20 to of at least two beta-promoters which are isomorphous with titanium and selected from the group consisting of vanadium, molybdenum, columbium and tantalum, up to 0. 3% carbon, up to 0.2% oxygen, up to 0.1% nitrogen, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta microstructure and a minimum bend ductility of not over 20 T.

10. An alloy consisting essentially ofabput: 20 .to 50% of vanadium, from at least 1% up to about 15 ,of at least one elementselected from the group consisting of additional beta-promoters and alpha-promoters which tend to stabilize the beta phase, balance titanium, said alloy being characterized by high thermal stability andin having a: substantially all-beta structure and a minimum bend ductility of not over ZO T.

11. An alloy consisting essentially of about: 20 to 50% of a plurality of beta-promoters, including at least 15% 12. of atleast one beta-promoter which is isomorphous with titanium, 1 to 15 of at least one alpha-promoter which tends to stabilize the beta phase, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

12. An alloy consisting essentially of about: 20 to 50% of a plurality of beta-promoters, including at least 15% of at least one beta-promoter which is isomorphous with titanium, 1 to 15% of at least one eutectoid beta-promoter, the total content of eutectoid beta-promoters present not exceeding the total content of isomorphous beta-promoters present, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ducti lity of not over 20 T.

13. An ailoy consisting essentially of about: 20 to 50% of a plurality of beta-promoters, including at least 15% of at least one beta-promoter which is isomorphous with titanium, l to 15 of at least one alpha-promoter which tends to stabilize the beta phase, 1 to 15 of at least one eutectoid beta-promoter, the total content of eutectoid beta-promoters present not exceeding the total content of the isomorphous beta-promoters present, balance titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

14. An alloy consisting essentially .of about: 10 to 50% of beta promoters, including at least 10% of at least one beta promoter which is isomorphous with titanium and selected from the group consisting of vanadium and molybdenum, 1 to 10% of at least one alpha-promoter which tends to stabilize the beta phase, balance substantially titanium, said alloy being characterized by high thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

15. An alloy consisting essentially of about: 10 to 50% of a plurality of beta promoters, including at least 10% of at least one beta promoter which is isomorphous with titanium and selected from the group consisting of vanadium and molybdenum, 1 to 10% of at least one alpha promoter which tends to stabilize the beta phase, 1 to 15 of at least one sluggishly eutectoid beta promoter selected from the group consisting of chromium, manganf's'e" and iron, balance substantially titanum, said alloy being characterized byrhigh thermal stability and in having a substantially all-beta structure and a minimum bend ductility of not over 20 T.

1 6. An alloy consisting essentially of about: 10 to 50% of beta promoters, including at least 10% of vanadium, 1 to 10% of at least one alpha promoter which tends to stabilize the beta phase, balance substantially titanium, said alloy being characterized by high thermal stability and inhaving a substantially all-beta structure and a minimum bend ductility of not over 20 T.

17. An alloy consisting essentially of about: 10 to 50% of beta promoters, including .at least 10% of vanadium, 1 to 8% of aluminum, balance substantially titanium, said alloy being characterized by high thermal stabilityand in having a substantially ail-beta structure and a minimum bend ductility of not over 20 T. i

18. An alloy consisting essentially of about: 20m 50% of a plurality of beta promoters, including at least 10% of at least one beta promoter which is isomorphous with titanium and selected from the group consisting of vana dium and molybdenum, balance substantially titanium, said alloy being characterized by high thermal stability and in having a substantiallyall-beta structure and a minimum bend ductility of not over 20 T.

(Re r nc on renewin Page) 13 References Cited in the file of this patent UNITED STATES PATENTS 2,554,031 Jafiee May 22, 1951 FOREIGN PATENTS 718,822 Germany Mar. 24, 1942 OTHER REFERENCES Project Rand, Titanium and Titanium Base Alloys,

USAF Project MX791 dated April 2, 1948; pages 3544 are relied on.

Titanium Report of Symposium, December 16, 1948, sponsored by the Ofiice of Naval Research, Dept. of the 5 Navy, Washington, D. C.; pages 110, 111, 128, 140 and 141 are relied on.

Product Engineering, vol. 20, No. 11, November 1949. page 149. 

1. AN ALLOY CONSISTING ESSENTIALLY OF ABOUT: 20 TO 50% OF AT LEAST ONE BETA-PROMOTER WHICH IS ISOMORPHOUS WITH TITANIUM AND FROM AT LEAST 1% UP TO ABOUT 15% OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF ADDITIONAL BETA-PROMOTERS AND ALPHA-PROMOTERS WHICH TEND TO STABILIZE THE BETA PHASE, BALANCE TITANIUM, SAID ALLOY BEING CHARACTERIZED BY HIGH THERMAL STABILITY AND IN HAVING A SUBSTANTIALLY ALL-BETA STRUCTURE AND A MINIMUM BEND DUCTILITY OF NOT OVER 20T. 